Method for refining ferrous metals



Feb. 16, 1954 1 l.. WHITNEY, JR 2,669,511

METHOD FOR REFINING FERROUS METALS Filed April 6, 1950 2 Sheets-Sheet lr/llll J Q www, om; mi W @m wm 25C@ |10 www @NNI www JHM- @w @l#.LLIFLI. l\ W y www f W Feb. 16, 1954 L. L. WHITNEY, JR

METHOD FOR REFINING FERRoUs METALS 2 Sheets-Sheet 2 Filed April 6, 1950l1. Y A

Nhoh n www @u 3M Patented Feb. 1.6, 1954 `UNITED STATES PATENT OFFICEMETHOD FOR REFINING FERRGUS METALS Loren L. Whitney, Jr., Alliance,lOhio Application April 6, 1950, Serial No. 154,330

(Cl. 'i5- 43) 3 Claims.

This invention relates to the melting and relining of ferrous metals andalloys charged into metallurgical furnaces, such as open hearth andelectrical furnaces, and more particularly to a novel method and meansfor accelerating the melting of the charge.

It will be understood that the production of any foundry is limited bythe output of its furnaces, and accordingly by decreasingthe timenecessary to melt the charge the output of the furnaces may be increasedthereby decreasing the cost of melting.

The present invention comprehends a novel method and means for reducingthe time for melting such a charge to about ten percent of the timerequired according to prior art practices.

A primary object of the present invention is to accelerate the meltingof a ferrous metal charge in a furnace by introducing a powder whichaccelerates oxidation of part of the charge necessary to provide heat tomelt the remainder thereof.

A further object of the invention is to devise a novel method and burnermeans for introducing the powder in such a manner as to afford maximumeffectiveness thereof.

The foregoing and further objects of the invention will become apparentfrom the following specification and the accompanying drawings, wherein:

Figure l is a diagrammatic view of an open hearth furnace, partly insection to illustrate the novel burner means applied thereto;

Figure 2 is a fragmentary enlarged View showing the burner means;

Figure 3 is an enlarged fragmentary, axial sectional view of the burnermeans shown in Figure 2; and

Figure 4 is a view similar to Figure 3 showing a modified burner means.

Describing the invention in detail and referring first to Figure l, aconventional open hearth furnace is somewhat diagrammaticallyillustrated at 2, although it will be understood that the invention isequally applicable to other types, such as electrical furnaces.

One of the novel burner devices generally designated 4 is insertedthrough an opening in each end wall 6 of the furnace above the adjacentend of the hearth 8 which is adapted to receive a charge (not shown) ashereinafter described. The burner 4 is supported by an adjusting bracketIIl hereinafter described in detail.

It may be noted that the furnace 2, which is of conventional design isprovided at each end thereof with a downtake flue I2 adapted todischarge outiiowing gases into a chamber I4 communicating with a flueI5 which discharges into a stack (not shown). The ue I5 is provided withthe usual checkerwork at I6 by which heat of outflowing gases isabsorbed to be later irnparted to air entering the furnace 2 as will beunderstood by those skilled in the art.

Referring now to Figure 2 which is an enlarged fragmentary view of thestructure shown in Figure l, it will be seen that the burner d comprisesa. pair of tubes I8 and Z0 mounted in the bracket I8, which is providedwith a shaft 24 connected thereto and threaded into a handwheel 26rotatably mounted in a bearing 28 supported by the end wall 6 of thefurnace 2. Thus as the shaft 2d is moved up and down by rotation of thehandwheel 2S the tubes I8 and 20 are adjustably rotated in unison abouttheir fulcrum points 3l) and 32 respectively where they are supportedwithin diagonal openings Sd and 36 of a hollow frame 3l having a waterinlet 38 and a water outlet 40. It will be understood that the tubes I8and 20 are loosely mounted in the bracket to accommodate the limitedrotation necessary for adjustment in service.

As shown in Figure 3, the tube I8 comprises a front section 42 and arear section 44 removably attached as by bolt and nut assemblies 4B. Therear section comprises a mixing chamber 48 connected to fuel oil line 50and a superheated steam line 52, whereby the oil and steam are mixedunder any desired pressure in the chamber 48 and are discharged througha pipe 511 into the furnace. The rear section 44 of the tube I8 `alsocomprises a passage or conduit accommodating a pipe 56 having acontainer 58 (Figure 2) of powdered catalyst, such as iron, connectedthereto by a port 68 in a fitting 82. A compressed air line is connectedto the fitting t2 and to the container 58 as at 5l beneath a plate 59,to blow the powdered catalyst from the container 5B and discharge thepowder into the furnace through the pipe 56. Pipe 56 extends looselywithin pipe 55. Pipe 68 constitutes a compressed air line whichdischarges compressed air into pipe of the tube I8 to pick up thecatalyst powder as it leaves tube 56 and diffuse it as it enters thefurnace.

The front section 42 of the tube I3 comprises radially inner and outerannular chambers 68 and 'I0 respectively, interconnected by ports 112 atthe forward end of the tube, said chambers being connected to waterinlet and outlet ports 'I3 and 14, respectively, by means of whichcoolant water may be circulated through said chambers.

The `lower tube 20 of the burner 4 comprises inner and outer annularchambers 16 and 'I8 interconnected at the forward end of the tube 20 andconnected, respectively, to inlet and outlet conduits 80 and 82 forcoolant water; and an oxygen pipe 84 extends centrally through the innerchamber 'I6 for delivering substantially pure oxygen to the furnaceunder any desired Referring now to Figure 4, a modified burner is shownwherein parts corresponding to those of Figure 3 are identified bycorresponding numerals. In Figure 4 it will be seen that the top tube i8contains two mixing chambers 48 each connected to a discharge pipe 54,an oil inlet line 50 and a superheated steam inlet line 52; and thebottom tube 20 contains the catalyst discharge pipe 56 extending throughthe oxygen pipe 84, to discharge the powder into the furnace at theforward end of the tube 20 where the catalyst and the pure oxygen fromthe pipe 84 are mixed as they enter the furnace.

It may be noted that the novel process hereinafter described may be usedin connection with the melting of iron and any alloys thereof, such asfor example stainless steel alloys; and the process although describedin connection with an open hearth Jfurnace may be also used in othertypes of melting devices such as electric furnaces, wherein theelectrode would preferably not be lowered until the novel processhereinafter described had leveled the charge.

In general, it has been discovered that by forcing oxygen of high purityand a powdered oxidizable material such as powdered iron, together witha flame fed by any of the conventional fuels such as fuel oil, pitch,natural gas, or blast furnace gas (or a flame of an electric arc, inwhich case the fuel would be electricity), the charge may be leveled inabout ten percent of the time normally required, whereupon the oxygenand powder may be discontinued and the heat continued by the fuel flamealone until ready for pouring.

Any one of the following metallic exothermic materials has provedeffective, because they iinmediately lundergo an exothermic reaction inthe presence of oxygen at the melting temperature of the charge, asdistinguished from materials which must undergo a roasting period beforethey are resolved into components capable of undergoing an exothermicreaction under these conditions. Preferably these exothermic materialsare in the form of fine powder, passing wire screen having 200 mesh persquare inch, although coarser powder may be used with diminishedeffectiveness, the maximum size of grain being that capable of passing ascreen having 100 mesh per square inch. For the purpose of thisdisclosure the term #metallic materials shall include silicon.

1. Iron of high purity 2. Cast iron 3. Iron and silicon mixture in anyratio 4. Iron, calcium, manganese, and silicon in any ratio 5. Iron,calcium, manganese, silicon and aluminum in any ratio The theory of thephenomenon is that the powder acts as an accelerating medium by burningto an oxide. This reaction is, of course, exothermic, producing a fewthousand B. t. u. However, this small amount of added heat could I notbe responsible for the unusual acceleration of melting, because theadditional heat, if proe duced by an increase of fuel and oxygen, willnot produce this result.

Theoretically one cubic foot of oxygen will oxidize 0.3 pound of ironproducing about 600 B. t. u. from 200 pounds of powder, yet it has beenfound that about 4,500,000 B. t. u. are required to process one ton ofsteel. It has also been discovered that after a temperature of 2700o F.is reached, about 5% of the charge must be oxidized to provide heat tomelt the remainder, much of this oxide being later reduced to metalliciron by the ore boil.

Thus according to the present invention, I have discovered that theinitial oxidization of the powder accelerates the reaction:

2 Fe (5% of charge) plus O2 2 FeO which produces suflicient heat totransform the remainder of the charge from thesolid to the molten state.

After the charge is under cover, that is when the charge is melted leveland a slag begins to form, the oxygen and powder are discontinued. Thisis the beginning of the refining period which is not affected by thenovel process. As is known, during the refining period the slag isintermittently fluXed with calcium fluoride and calcined lime to removeundesirable elements such as phosphorus and sulphur. Either iron ore orlanced oxygen is employed in the usual manner to remove carbon to thedesired tapping range. On completion of the refining period which ordinnarily is completed within about two hours, molten metal may, ifdesired, be deoxidized by any of the usual agents, such as l5 ferrosilicon, ferro manganese, or Silico-manganese.

One example of the novel process as applied to a 61,000 pound charge inan open hearth furnace follows:

1. The furnace was charged in about 35 minutes. This step includedplacing a protective layer of flat scrap on the bottom of the hearth,then placing a layer of lime on the flat scrap, and then charging thebalance consisting of scrap and pig iron. An oil ame atomized withsuperheated steam was applied by the burner tube i8 to the scrap and pigiron for the purpose of preheating as it was charged on top of the lime.Oxygen at a pressure of 100 p. s. i. was discharged by pipe 84 duringthe last 14 minutes of the charging period, to obtain a higher degree ofpreheat.

2. Immediately upon completion of the charge, oxygen was forced into thefurnace through pipe 84, and powdered iron of high purity was forcedthrough pipe 56 by compressed air in line S4 at a pressure of the orderof ninety pounds per square inch. At the end of thirteen minutes thecharge was melted level and a molten slag had formed over the top of themetal.

3. The balance of the heat constituting the reiining period wascompleted using an oil flame only, and the oxygen and iron powder wasdiscontinued.

Total oxygen time 27 minutes Total oxygen consumpticn 5,530 cubic feetOxygen rate 13,000 cubic feet per hour Total iron powder tirne r 13minutes Total iron powder consumptionpounds Iren powder rate 7.3 poundsper minute It will be understood by those skilled in the art thatordinarily about two and one half hours A are required to melt thecharge level and thus' a it will be seen that the above describedprocess reduces this period of the heat to about ten percent of the timeformerly required.

Similar results have been obtained using the other agents heretoforedescribed, and I have found that any powder which will immediatelyoxidize at l000 F. will greatly reduce the melt ing time.

I claim:

1. In a method of refining a charge of ferrous metal or alloy thereof,in a metallurgical furnace, the steps of first inserting said chargeinto the furnace, then melting sai-d charge by heating it to the meltingtemperature thereof While simultaneously directing against said charge astream of substantially pure oxygen and a stream of powdered iron andthen after the charge has melted substantially level terminating theflow of oxygen and powdered iron while refining the charge by continuingto heat the same.

2. A method of refining ferrous or alloy thereofcomprising inserting acharge of said metal or alloy into a furnace, then melting the charge bydirecting a llame, a stream of substantially pure oxygen, and a streamof powdered iron against the charge and then after the charge is meltedlevel terminating the streams of oxygen and powdered iron whilecontinuing to heat the charge With said flame until the charge has beenrefined.

3. In a method of refining a charge of ferrous metal or alloy thereof ina metallurgical furnace, the steps of first inserting said charge intothe furnace, then melting said charge by directing a name against saidcharge While simultaneously directing against said charge a stream ofsubstantially pure oxygen and While simultaneously directing againstsaid charge a stream of exothermic metallic powder which immediatelyundergoes an exothermic reaction at the melting temperature of saidcharge in an amount which is sufficient to reduce 'the melting time ofsaid charge, and then, after the charge has melted substantially level,terminating the flow of oxygen and powder while refining the charge bycontinuing to heat the same With said flame.

LOREN L. WHITNEY, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 103,940 Menne July 1, 1902 968,350 Harrison Aug. 23, 19101,030,152 Barbansen et al. June 18, 1912 1,825,841 Zifferer Oct. 6, 19312,182,498 Longenecker Dec. 5, 1939 2,286,191 Aitchison et al, June 16,1942 2,362,085 Morgan Nov. '7, 1944 2,446,511 Kerry et al. Aug. 3, 19482,451,422 Wagner Oct. 12, 1948 2,466,258 Morgan Apr. 5, 1949 2,470,999Meincke May 24, 1949 2,491,440 Bodecker Dec. 13, 1949 2,515,670 Slottmanet al July 18, 1950 OTHER REFERENCES Open Hearth Proceedings, vol. 31,pages 91 to 94, inclusive. Published in 1948 by the A. I. M. E., NewYork, New York.

1. IN A METHOD OF REFINING A CHARGE OF FERROUS METAL OR ALLOY THEREOF, IN A METALLURGICAL FURNACE, THE STEPS OF FIRST INSERTING SAID CHARGE INTO THE FURNACE, THEN MELTING SAID CHARGE BY HEATING IT TO THE MELTING TEMPERATURE THEREOF WHILE SIMULTANEOUSLY DIRECTING AGAINST SAID CHARGE A STREAM OF SUBSTANTIALLY PURE OXYGEN AND A STREAM OF POWDERED IRON AND THEN AFTER THE CHARGE HAS NITROGEN, MELTED SUBSTANTIALLY LEVEL TERMINATING THE FLOW 